1. FIELD OF THE INVENTION
The present invention relates to an intake member of a resin including a generally cylindrical main section of a resin, and a subsidiary section of a resin which is integrally connected to an outer periphery of the main section, and a process for producing the same.
2. DESCRIPTION OF THE RELATED ART
A process for forming a mixture body block of a carburetor which is an intake member for an engine, using a resin by injection molding, has been proposed in Japanese Patent Application Laid-open No. 62-196115.
A member such as the mixture body block requires less accuracy in dimension and hence, could be formed from a resin which is generally not so accurate in dimension, as compared with a metal. A member such as a throttle body which is an intake member for an engine, however, requires a sufficiently high dimensional accuracy at its inner peripheral surface, because a clearance between the inner peripheral surface of such member and an outer peripheral surface of a throttle valve accommodated in the throttle body and turned therein exerts a large influence to the idling performance of the engine.
Accordingly, it is an object of the present invention to provide a process for forming an intake member for an engine that requires a high accuracy in dimension, from a resin by molding, and an intake member of a resin produced in such process. To achieve the above object, according to a first aspect and feature of the present invention, there is provided a process for producing an intake member of a resin by injection molding, in which the intake member includes a generally cylindrical main section of a resin, and a subsidiary section of a resin integrally connected to an outer periphery of the main section, wherein the process comprises a primary molding step of forming the main section in a primary molding die, and a secondary molding step of subsequently inserting the formed main section into a secondary molding die to form the subsidiary section integrally with the main section in the secondary molding die.
With the above feature, the main section formed at the primary molding step is generally cylindrical and has no large difference in thickness among its respective portions. Therefore, the shrinkage and warping generated during cooling can be suppressed to the minimum, thereby enabling the main section to be provided with a higher roundness or circularity. Moreover, the subsidiary section integrally connected to an outer periphery of the cylindrical main section is formed by the secondary molding step subsequent to the primary molding step and therefore, an intake member of resin having a desired shape can be finally produced.
According to a second aspect and feature of the present invention, in addition to the first feature, at the primary molding step, a molten resin is supplied through a disk gate to axially one end of a cavity of the primary molding die.
With the above feature, by supplying the molten resin through the disk gate to axially one end of the cavity in the primary molding die at the primary molding step, the resin can be poured uniformly into the cavity to prevent the orientation of a filler contained in the resin, thereby producing an intake member of a resin having a higher accuracy.
According to a third aspect and feature of the present invention, in addition to the first or second feature, the die temperature at an inner peripheral surface of the main section is set lower than the die temperature at an outer peripheral surface of the main section at the primary molding step.
With the above feature, the die temperature at the inner peripheral surface of the main section is set lower than die the temperature at the outer peripheral surface of the main section. Therefore, the inner peripheral surface of the main section can be cooled in advance to prevent the generation of shrinkage and warping, leading to a further increased roundness of the inner peripheral surface.
According to a fourth aspect and feature of the present invention, in addition to the first or second feature, the intake member of resin is a throttle body having a throttle valve turnably supported therein.
With the above feature, since the intake member of the resin is the throttle body, the roundness of the throttle body can be increased, whereby the clearance between the inner peripheral surface of the throttle body and an outer periphery of the throttle valve can be uniformized, leading to an enhanced idling performance of an engine.
According to a fifth aspect and feature of the present invention, in addition to the fourth feature, a pair of boss portions for supporting a stem portion of the throttle valve is integrally formed on the main section at the primary molding step.
With the above feature, when the main section is formed, the pair of boss portions for supporting the stem portion of the throttle valve is formed on the main section. Therefore, not only the accuracy of the boss portions can be enhanced, but also the number of forming the boss portions can be suppressed to the minimum.
According to a sixth aspect and feature of the present invention, in addition to the first feature, different types of resin materials are used for forming the main section and the subsidiary section.
With the above feature, the freedom degree of selecting the material according to the demand for a dimensional accuracy and the demand for a reduction in cost is increased.
According to a seventh aspect and feature of the present invention, in addition to the first feature, the intake member is integrally formed by injection-molding a super engineering plastic as a resin material in a cavity of the primary molding die and injection-molding a general-purpose engineering plastic as a resin material in a cavity of the secondary molding die.
With the above feature, the demands for a dimensional accuracy and a reduction in cost can be reconciled by injection-molding the super engineering plastic or the general-purpose engineering plastic depending on each portion in the intake member.
According to an eighth aspect and feature of the present invention, there is provided a process for producing an intake member of a resin by injection molding, in which the intake member includes a generally cylindrical main section, and a subsidiary section integrally connected to an outer periphery of the main section, wherein the process comprises a primary molding step of forming the main section in a primary molding die, and a secondary molding step of subsequently inserting the formed main section into a secondary molding die to form the subsidiary section integrally with the main section in the secondary molding die, wherein the same type of a resin material is used for forming the main section and the subsidiary section.
With the above feature, the main section formed at the primary molding step is generally cylindrical and has no large difference in thickness among its respective portions. Therefore, the shrinkage and warping generated during cooling can be suppressed to the minimum, thereby enabling the main section to be provided with a higher roundness or circularity. Moreover, the subsidiary section integrally connected to an outer periphery of the cylindrical main section is formed at the secondary molding step subsequent to the primary molding step and therefore, an intake member of resin having a desired shape can be finally produced. In addition, the same type of resin material is used for forming the main section formed at the primary molding step and the subsidiary section formed at the secondary molding step. Therefore the main section and the subsidiary section can be easily integrally formed in a satisfactorily conformed fashion, leading to a further increased roundness of the main section. Moreover, one type of resin material may be injected and hence, an injection molding apparatus can be simplified to reduce the equipment cost.
According to a ninth aspect and feature of the present invention, in addition to the eighth feature, the resin material is a super engineering plastic or a general-purpose engineering plastic.
With the above feature, the performance and the cost can be freely selected depending on the degree of priority by properly using the super engineering plastic which provides an enhanced dimensional accuracy in a product, but is expensive, or the general-purpose engineering plastic which provides a slightly lower dimensional accuracy in a product but is inexpensive.
According to a tenth aspect and feature of the present invention, there is provided an intake member of a resin including a generally cylindrical main section of a resin, and a subsidiary section of a resin integrally connected to an outer periphery of the main section, wherein the main section is formed in a primary molding die at a primary molding step, and subsequently the formed main section is inserted into a secondary molding die in which the subsidiary section is formed integrally with the main section at a secondary molding step.
With the above feature, the main section primarily formed is generally cylindrical and has no large difference in thickness among its respective portions. Therefore, the shrinkage and warping generated during cooling can be suppressed to the minimum, thereby enabling the main section to be provided with a higher roundness or circularity. Moreover, the subsidiary section integrally connected to an outer periphery of the cylindrical main section is formed at the secondary molding step subsequent to the primary molding step and therefore, an intake member of resin having a desired shape can be finally produced.
According to an eleventh aspect and feature of the present invention, in addition to the tenth feature, at the primary molding step, a molten resin is supplied through a disk gate to axially one end of a cavity of the primary molding die.
With the above feature, by supplying the molten resin through the disk gate to axially one end of the cavity of the primary molding die at the primary molding step, the resin can be poured uniformly into the cavity to prevent the orientation of a filler contained in the resin, thereby producing an intake member of resin having a higher accuracy.
According to a twelfth aspect and feature of the present invention, in addition to the tenth or eleventh feature, the die temperature at an inner peripheral surface of the main section is set lower than the die temperature at an outer peripheral surface of the main section at the primary molding step.
With the above feature, the temperature of the die at the inner peripheral surface of the main section is set lower than the temperature of the die at the outer peripheral surface of the main section. Therefore, the inner peripheral surface of the main section can be cooled in advance to prevent the generation of shrinkage, leading to a further increased roundness of the inner peripheral surface.
According to a thirteenth aspect and feature of the present invention, in addition to the tenth or eleventh feature, the intake member of resin is a throttle body having a throttle valve turnably supported therein.
With the above feature, since the intake member of resin is the throttle body, the roundness of the inner peripheral surface of the throttle body can be enhanced, whereby the clearance between the inner peripheral surface of the throttle body and an outer periphery of the throttle valve can be uniformized, leading to an enhanced idling performance of an engine.
According to a fourteenth aspect and feature of the present invention, in addition to the thirteenth feature, a pair of boss portions for supporting a stem portion of the throttle valve is integrally formed on the main section at the primary molding step.
With the above feature, when the main section is formed, the pair of boss portions for supporting the stem portion of the throttle valve is formed on the main section. Therefore, not only the accuracy of the boss portions can be enhanced, but also the number of steps for forming the boss portions can be suppressed to the minimum.
According to a fifteenth aspect and feature of the present invention, in addition to the tenth feature, different types of resin materials are used for forming the main section and the subsidiary section.
With the above feature, the freedom degree of selecting the resin material according to the demand for a dimensional accuracy and the demand for a reduction in cost is increased.
According to a sixteenth aspect and feature of the present invention, in addition to the tenth feature, the intake member is integrally formed by injection-molding a super engineering plastic as a resin material in a cavity of the primary molding die and injection-molding a general-purpose engineering plastic as a resin material in a cavity of the secondary molding die.
With the above feature, the demands for a dimensional accuracy and a reduction in cost can be reconciled by injection-molding the super engineering plastic or the general-purpose engineering plastic depending on each portion in the intake member.
According to a seventeenth aspect and feature of the present invention, there is provided an intake member of a resin including a generally cylindrical main section of a resin, and a subsidiary section of a resin integrally connected to an outer periphery of the main section, wherein the main section is formed in a primary molding die at a primary molding step, subsequently, the formed main section is inserted into a secondary molding die, in which the subsidiary section is formed integrally with the main section at a secondary molding step, wherein the same type of a resin material is used for forming the main section and the subsidiary section.
With the above feature, the main section primarily formed is generally cylindrical and has no large difference in thickness among its respective portions. Therefore, the shrinkage and warping generated during cooling can be suppressed to the minimum, thereby enabling the main section to be provided with a higher roundness or circularity. Moreover, the subsidiary section integrally connected to an outer periphery of the cylindrical main section is formed by the secondary molding step subsequent to the primary molding step and therefore, an intake member of resin having a desired shape can be finally produced. In addition, the same type of resin material is used for forming the main section formed at the primary molding step and the subsidiary section formed at the secondary molding step. Therefore, the main section and the subsidiary section can be easily integrally formed in a satisfactorily conformed fashion, leading to a further increased roundness of the main section. Moreover, one type of resin material may be injected and hence, an injection molding apparatus can be simplified to reduce the equipment cost.
According to an eighteenth aspect and feature of the present invention, in addition to the seventeenth feature, the resin material is a super engineering plastic or a general-purpose engineering plastic.
With the above feature, the performance and the cost can be freely selected depending on the degree of priority by properly using the super engineering plastic which provides an enhanced dimensional accuracy of a product, but is expensive, or the general-purpose engineering plastic which provides a slightly lower dimensional accuracy of a product but is inexpensive.